compare textbox value with DataTable column

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I am trying to delete some data in column (Delta_sigma) by comparing it with value entered in textbox but i get error Cannot perform '<' operation on System.Double and System.String.

 DataColumn Delta_sigma = table1.Columns.Add("Delta_Sigma", typeof(double));

Delta_sigma.Expression = "(Convert(Median,'System.Double') -                                        Convert(Median_Refrence,'System.Double')) / (sigma_Refrence)";
 
double delta_sigma_critical = double.Parse(textBox1.Text);


DataRow[] rows4;
 rows4 = table1.Select("  Delta_sigma < delta_sigma_critical ");
            foreach (DataRow r in rows4)
                r.Delete();

Posted 24-Apr-14 5:27am

FarhanShariff

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2 solutions

Solution 1

Quote:
Cannot perform '<' operation on System.Double and System.String.

Quite clear. You cannot compare data of different types.

So, try to compare data with same type.

Posted 24-Apr-14 6:43am

Tadit Dash (ତଡିତ୍ କୁମାର ଦାଶ)

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FarhanShariff 25-Apr-14 3:32am

I know that how to do that?

Tadit Dash (ତଡିତ୍ କୁମାର ଦାଶ) 25-Apr-14 3:49am

I guess it should look like...

rows4 = table1.Select("Delta_sigma < " + delta_sigma_critical);
foreach (DataRow r in rows4)
r.Delete();

Try and let me know.

FarhanShariff 25-Apr-14 4:43am

select cannot use 'external' varibale

Tadit Dash (ତଡିତ୍ କୁମାର ଦାଶ) 25-Apr-14 7:09am

Okay. I think you did it in a other way by looping. Good. :)

FarhanShariff 25-Apr-14 7:16am

please check this http://www.codeproject.com/Questions/764845/compare-textbox-value-with-DataTable-column

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FarhanShariff · Accepted Answer · 2014-04-24T22:44:00

C#

double delta_sigma_critical = double.Parse(textBox1.Text);

for(int i = table1.Rows.Count - 1; i >= 0; i--)
{
   double d = Convert.ToDouble(table1.Rows[i]["Median"].ToString()) - Convert.ToDouble(table1.Rows[i]["Median_Refrence"].ToString());
   d /= Convert.ToDouble(table1.Rows[i]["sigma_Refrence"].ToString());
   if (d < delta_sigma_critical) table1.Rows.RemoveAt(i);
}